This invention relates to a method and apparatus for treating yarn with a pressured fluid in a jet. More particularly, it concerns a baffle and deflector arrangement at the outlet end of a yarn texturing jet.
Fluid jet processess are known for texturing or bulking yarn that employ both movable and fixed baffles positioned at various distances from the outlet end of the jet and at various angles to the yarn path to deflect yarn and fluid from a straight path as they leave the jet.
In making a yarn having crunodal loops, the texturing jet must forward the overfed yarn under sufficient tension to keep the yarn from wrapping on the feed rolls, and this tension is provided by the drag of the pressurized air which is moving much faster than the yarn. The air opens the yarn, whips the filaments about, forms loops in the filaments, then entangles them together into a structure which can retain the loops under the tensions which such yarns encounter when made into fabrics. The tension must be low at the jet exit to accumulate loops and form the entangled structure. Immediately thereafter, higher tension is desired to tighten the entangled structure and stabilize it.
In order that the yarn texture be uniform, the tension on the yarn should be as uniform as possible in the low tension zone near the jet exit and in the higher tension stabilizing zone between the jet exit and the yarn takeaway. If tensions in these zones vary, the texture will be non-uniform along the end of the yarn. It can be seen that, if the yarn oscillates between the two zones, the tensions in both are nonuniform. In the case of a high speed process where high pressure air is required to give sufficient loops and entanglement, it is particularly difficult to provide stable, uniform tensions of the desired degrees.
A baffle against which the air and yarn impinge is often provided at the jet exit to provide a stagnant air zone and to change the direction of yarn movement abruptly. Such baffles are especially necessary at high speeds and pressures. pressure. However, with known cylindrical baffle arrangements, the air divides around the baffle, and the portion of the air which follows the yarn continues to exert tension. Other portions of the air stream impinge on the yarn on the far side of the baffle and shake it so as to produce nonuniform texture.
In the present invention, the majority of the air follows the upper surface of a cylindrical baffle while the yarn moves around the lower surface of the baffle. The air stream exerts drag on the baffle so that if the baffle is a low-friction roller, it will rotate in a direction counter to the yarn movement. This rotation further reduces the tension in the yarn at the jet exit and increases the tension between the baffle and the yarn take-away. A deflector positioned above the baffle prevents the air stream from disturbing the yarn as it leaves the baffle on the far side.